[PATCH v6 18/27] powerpc: define syscall_get_error()

From: Dmitry V. Levin
Date: Thu Dec 13 2018 - 12:23:18 EST


syscall_get_error() is required to be implemented on this
architecture in addition to already implemented syscall_get_nr(),
syscall_get_arguments(), syscall_get_return_value(), and
syscall_get_arch() functions in order to extend the generic
ptrace API with PTRACE_GET_SYSCALL_INFO request.

Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Elvira Khabirova <lineprinter@xxxxxxxxxxxx>
Cc: Eugene Syromyatnikov <esyr@xxxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
---

Notes:
v6: unchanged

v5:
This change has been tested with
tools/testing/selftests/ptrace/get_syscall_info.c and strace,
so it's correct from PTRACE_GET_SYSCALL_INFO point of view.

This cast doubts on commit v4.3-rc1~86^2~81 that changed
syscall_set_return_value() in a way that doesn't quite match
syscall_get_error(), but syscall_set_return_value() is out
of scope of this series, so I'll just let you know my concerns.

arch/powerpc/include/asm/syscall.h | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index ab9f3f0a8637..1d03e753391d 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -39,6 +39,16 @@ static inline void syscall_rollback(struct task_struct *task,
regs->gpr[3] = regs->orig_gpr3;
}

+static inline long syscall_get_error(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ /*
+ * If the system call failed,
+ * regs->gpr[3] contains a positive ERRORCODE.
+ */
+ return (regs->ccr & 0x10000000UL) ? -regs->gpr[3] : 0;
+}
+
static inline long syscall_get_return_value(struct task_struct *task,
struct pt_regs *regs)
{
--
ldv